Return-Path: Received: (qmail 16686 invoked from network); 6 Dec 2000 20:40:24 -0000 Received: from unknown (HELO murphys-inbound.servers.plus.net) (212.159.14.225) by excalibur.plus.net with SMTP; 6 Dec 2000 20:40:24 -0000 Received: (qmail 24631 invoked from network); 6 Dec 2000 20:35:28 -0000 Received: from unknown (HELO post.thorcom.com) (212.172.148.70) by murphys with SMTP; 6 Dec 2000 20:35:28 -0000 Received: from majordom by post.thorcom.com with local (Exim 3.16 #1) id 143lAz-0006dQ-00 for rsgb_lf_group-outgoing@blacksheep.org; Wed, 06 Dec 2000 20:28:29 +0000 Received: from mail6.svr.pol.co.uk ([195.92.193.212]) by post.thorcom.com with esmtp (Exim 3.16 #1) id 143lAx-0006dL-00 for rsgb_lf_group@blacksheep.org; Wed, 06 Dec 2000 20:28:28 +0000 Received: from modem-200.aluminum.dialup.pol.co.uk ([62.136.12.200] helo=default) by mail6.svr.pol.co.uk with smtp (Exim 3.13 #0) id 143lAs-0001DN-00 for rsgb_lf_group@blacksheep.org; Wed, 06 Dec 2000 20:28:22 +0000 Message-ID: <001601c05fc2$6373c700$c80c883e@default> From: "MAL HAMILTON" To: "rsgb" Subject: LF: keep cool Date: Wed, 6 Dec 2000 20:10:31 -0000 MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1; format=flowed Content-Transfer-Encoding: 8bit X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 4.72.3110.5 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group Sender: My experience is to use air cored coils in preference to toroid types if possible for high power applications. If you must use toroids keep them cold by using a good high pressure fan or preferably insert the LPF into a portable refrigerator. (available at Halfords) In LP filter applications running the new big super amplifiers of several k/watts use forced water cooling coils and large home made fibre glass/copper clad board and teflon insulation for the capacitors. This assumes you are using a square wave derived TX with very strong odd order harmonics 3/5/7 th etc. Sheets of copper clad teflon or fibre glass board are available in 8 feet x 4 feet size. de G3KEV